Process monitoring system for lithography lasers

ABSTRACT

A system for a monitoring lithography lasers at integrated circuit fabrication plants. Each laser at each fabrication plant has associated with it a terminal server. With respect to each fabrication plant a central control server unit is in communication with each of the lasers through a local area network. Information from the lasers is collected by the central control server unit and the information is used to provide summary information which is made available in a web site format to interested parties having access authorization.

[0001] This application is a continuation-in-part of Ser. No.09/505,233, filed Feb. 16, 2000. The present invention relates tomonitoring systems and in particular to monitoring systems for lasers.

BACKGROUND OF THE INVENTION

[0002] The fabrication of integrated circuits is typically accomplishedusing a lithographic process in which a stepper or scanner machine isused to print integrated circuits on silicon wafers. In state of the artfabrication plants, the light sources for this lithographic process areexcimer lasers, most of which are narrow band KrF excimer lasersoperating at a wavelength of about 248 nm. In the future, greaterresolution, than is possible with the 248 nm wavelength light will beprovided by an industry shift to ArF excimer lasers operating at about193 nm and F₂ excimer lasers operating at about 152 nm.

[0003] Since the fabrication lines including the stepper/scannermachines and their associated laser light sources are very expensive andthe integrated circuits they produce are very valuable, the integratedcircuit fabrication lines typically operate almost continuously, “roundthe clock”, 24 hours a day, 7 days per week 365 days per year with theminimum possible down time for maintenance. Therefore, great efforts gointo building and servicing the fabrication line equipment, includingthe excimer lasers, to minimize down time, especially unscheduled downtime. As a result, lithography excimer lasers are expected to have “downtime” of much less than 1%.

[0004] In addition, the quality of the integrated circuits produced onthese fabrication lines is to a large extent dependent on the quality ofthe laser beam produced by the laser

[0005] The beam as indicated above is typically line narrowed and theenergy of each pulse is carefully controlled. Beam quality specificationparameters of centerline wavelength, bandwidth and pulse energy aretypically monitored for each pulse which in state of the art lithographylasers operate at pulse rates of between 1,000 and 2,500 pulses persecond. Beam specifications for a typical KrF excimer laser might be:Wavelength variation (within a 30 pulse window) = ±0.07 pm Wavelengthsigma (i.e., standard deviation) = ±0.06 pm Bandwidth (less than) =  0.6pm Dose variation (within a 30 pulse window) = 0.4 percent Energy Sigma(within a 30 pulse window) =  12 percent Energy Variation (within a 30pulse window) = 7.5 percent

[0006] These specifications are examples of the type of qualitystandards which are applied to determine if a laser's performance passesan acceptance test prior to shipment from the laser fabrication plant.

[0007] During operation of the integrated circuit fabrication line,energy, center wavelength, and bandwidth are monitored and energy andcenterline wavelength are controlled with automatic computer basedfeedback controls. Various methods are used by the operators of thefabrication lines to control the quality of the laser beam and to makedecisions as to when adjustments, maintenance or equipment replacementis necessary. These decisions are often difficult to make when beamquality deteriorates because shutting down a production line for repairsusually involves production losses which increase unit production costsof the integrated circuits. On the other hand, continuing to producewith less than ideal beam quality results in reduced quality.

[0008] U.S. Pat. No. 5,646,954 (incorporated herein by reference)describes a prior art maintenance strategy control system and monitoringmethod for improving performance reliability of excimer laserlithography light sources. This system uses microprocessors to monitorlaser pulses and to predict based on usage values when maintenance andequipment replacement should be scheduled. Lithography lasers aretypically built in modular form so that an entire module is quicklyreplaced with a spare module whenever there is a failure within themodule. The replaced module is then returned to the factory. Thereusable parts in it are recycled into newly manufactured modules.Examples of such modules include chamber modules comprising the laserchamber and associated components, stabilization modules comprising awavemeter for stabilizing the wavelength and pulse energy of the laserbeam and a line narrowing module (LNM) for narrowing the bandwidth ofthe laser beam and controlling the wavelength of the beam.

[0009] Control of laser beam quality is very important to maintaininghigh quality integrated circuit production. State of the art lithographylasers such as KrF excimer lasers comprise three informationcontrol-data ports:

[0010] (1) a stepper/scanner port through which the stepper/scannercomputer controller issues firing commands to the laser computer.

[0011] (2) a serial port for a laser control device in the shape of apaddle and called a paddle through which laser operators send serialcommands to the laser to control laser parameters such as targetwavelength, pulse energy or makes adjustments to parameters such as gasmixtures.

[0012] (3) An RS-232 diagnostic port used by field engineers to collectparametric data from the laser computer.

[0013] A typical current process for collecting and processing data fromlithography lasers by the laser manufacturer involve the followingsteps:

[0014] a) Field engineers from the laser manufacturer physicallydownload the data from the lithography lasers every week

[0015] b) This data is stored in the form of ASCll flat files and thensent by E-mail to laser manufacturer for further processing.

[0016] c) This E-mail based program has been in use for 3 years, whichparses data files of E-mails and saves them in a server.

[0017] d) This data is viewed/massaged by experienced factory technicalsupport personnel for discrepancy.

[0018] e) Ad-hoc queries are generated by user(s) based on the data inSQL Server Database for historical analysis.

[0019] f) The entire process is time sensitive (e.g. certain queriestake between 7 to 8 minutes for processing).

[0020] The following limitations exist since the current process ismanual in nature:

[0021] a) Field engineers must be physically present in the clean roomenvironment at the integrated circuit fabrication plant to download thisdata every week. Hence, this process cannot be done daily but has to bescheduled with the customer/field engineers. The data currently is beingcollected every week.

[0022] b) The data is not real time in any nature and by the time it isprocessed the data may be more than a week old.

[0023] c) There is no continuous status reporting.

[0024] d) Training of field engineers to download the data in properformat is necessary.

[0025] e) There are no automatic alerts to concerned personnel.

[0026] f) The entire process has a degree of uncertainty in operatingthese laser machines and represents substantial overhead cost to boththe laser supplier and the fabrication plant.

[0027] What is needed is a better system for monitoring lithographylasers.

SUMMARY OF THE INVENTION

[0028] The present invention provides a system for a monitoringlithography lasers at integrated circuit fabrication plants. Each laserat each fabrication plant has associated with it a terminal server. Withrespect to each fabrication plant a central control server unit is incommunication with each of the lasers through a local area network.Information from the lasers is collected by the central control serverunit and the information is used to provide summary information which ismade available in a web site format to interested parties having accessauthorization.

[0029] A principal function of the present invention is data acquistion.Monitors on the lasers record an enormous amount of data. For example,each laser pulse is monitored for pulse energy, wavelength, bandwidthand charging voltage. Since a state of the art laser typically operatesat 2000 Hz at duty cycles of about 20 percent, just these parametersrepresent 1600 values collected each second and since operation isaround the clock this data amounts to about 138 million values ofprimary laser data per day. In addition, the laser calculates otherperformance values from this primary data. The calculated values includestandard deviation values of both wavelength and pulse energy for smallgroups of data. The laser also calculates a dose variation value fordesignated groups of pulses referred to as “windows” of pulses. Inaddition, other laser parameters are monitored very frequently and maybe recorded as often as desired. These other parameters include varioustemperature values, laser gas pressure and fan speed.

[0030] Typically the lithography lasers are operated in bursts mode inwhich short bursts of pulses (such as 200 pulses) are produced (duringwhich time a single dye spot on a wafer is illuminated) followed by anidle time of a fraction of a second during which time the stepper orscanner moves to a different dye spot. After all the dye spots on awafer are illuminated there is a longer idle time of a few secondsduring which time a new wafer is moved into place. The laser monitorsthis pattern and the present system is capable of documenting each andevery pulse of every burst along with the idle times. In addition anydesired summaries, compilations, reports, tables which are aggregates orcomparisons of the data may be calculated and stored and made availableon an almost real-time basis.

[0031] Charts could include:

[0032] 1) For each laser up-time (or down time) on a monthly basis

[0033] 2) For each laser duty cycle during up-times

[0034] 3) For each chamber integrated pulse count since last chamberreplacement

[0035] 4) For each module (such as LNP, Power supply module, commutatormodule, compression lead module, gas module) integrated pulse count (ordays) since last module replacement

[0036] 5) For each laser at specified time intervals: wavelengthmonitor, wavelength sigma, average bandwidth, dose variation, energysigma and energy variation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a chart showing the general layout of a preferredembodiment of the present invention.

[0038]FIGS. 2 through 5 are copies of computer printouts showing thegeneral appearance of typical web pages which were created with aprototype embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Preferred Embodiment

[0039] A first preferred embodiment of the present invention can bedescribed by reference to the drawings. A general outline of a processmonitoring system for monitoring lithography lasers in integratedcircuit fabrication plants is shown in FIG. 1.

Lasers

[0040] Lasers 2 in this preferred embodiment are excimer lasers which,in a specific integrated fabrication, may be approximately 20 lasersmade up of a combination of models of KrF lasers such as Cymer 5000series and Cymer 6000 series lasers available from Cymer, Inc. withoffices in San Diego, Calif. These lasers operate at repetition rates ofabout 1000 Hz or 2000 Hz producing laser pulses of about 10 mJ perpulse. These are the ultraviolet light sources for scanner and steppermachines which produce integrated circuits on silicon wafers.

Interface

[0041] An RS-232C interface port 4 provides for communication betweenthe laser controls and the monitoring equipment shown in FIG. 1.

Terminal Server

[0042] Each laser has associated with it a terminal server 6 having aunique internet address. In the preferred embodiment, the terminalserver 6 is a standard server Model LE 995A-R3 available from Blackbox,Inc.

Fabrication Plant Central Control Server

[0043] In this preferred embodiment each integrated circuit fabricationplant forming part of the system is served with a single fabricationplant central control server 8. The server 8 communicates with eachlaser 2 through the fabrication plant's local area network (LAN) 7 asshown in FIG. 1. The preferred minimum requirements for the server areas follows:

[0044] Processor: Pentium 700 MHz or higher, dual processor system

[0045] RAM: 2 Gb

[0046] Hard Disk: 400 Gb

[0047] UPS

[0048] Backup Tape Drive—400 Gb

[0049] A preferred server meeting these requirements would be a serverwithin the HP LH 6000 Series available from Hewlett Packard.

[0050] The above system will be sufficient for a fabrication plantwhere:

[0051] a) data is stored for up to 6 months

[0052] b) the number of lasers are 20 or less.

The Internet

[0053] As shown in FIG. 1 in this preferred arrangement the operators ofthe fabrication plant have erected a fabrication plant firewall 12between its communication network and the outside world to protectagainst unauthorized access to the information on its LAN. The lasermanufacturer which in this case is responsible for assuring that thelasers 2 comply with agreed upon performance standards and also hascontractual obligations with respect to performance of the lasers ispermitted limited access to information collected by the monitoringsystem at the fabrication plant. This limited access is provided (asagreed between the laser manufacturer and the operator of thefabrication plant) through the Internet. However, both organizationshave provided firewalls shown as 12 for the fabrication plant and 11 forthe manufacturer.

[0054] Thus, in a particular preferred embodiment, certain types of data(previously agreed upon) can be stored in server 8 in a web site typeformat and down loaded by manufacturer through the manufacturer'sInternet server 16 to any of several central processing units (notshown) at the manufacturer's facilities.

Control and Monitoring Programs

[0055] The central control server 8 in this preferred embodimentutilizes the following commercially available software packages:

[0056] a) Operating System—Linux 6.2 Deluxe Version with X11 R6

[0057] b) Database Storage and Retrieval—Oracle 8I Standard Edition

[0058] c) Web Server—Tomcat Version 3.1

Programming

[0059] Linux CVS/RCS program is used to program the Linux operatingsystem 8 for this application. A GNU toolset is used to create programlibraries which permit the various programs to be modular. Programlibraries include: shared libraries, static libraries and dynamicallyloaded libraries.

Computer Program for Central Control

[0060] The software for operating system 8 is preferably created inmodular form. There are four primary software modules: the dataacquisition module, the parser module, the database module and the userinterface module.

The Data Acquisition Module

[0061] The data acquisition module consists of a set of programsperforming the task of gathering data from lasers 2 and sending the datato the paser module for further processing. The communication is throughthe terminal server 6 and the RS232C interface 4 as shown in FIG. 1.

[0062] The data acquisition module comprises the following softwarecomponents:

[0063] Laser Read and Write

[0064] Command Write to Lasers

[0065] Command Write Queue

[0066] Data Read from Lasers

[0067] Master Scheduler

[0068] Interface to Parser Program

[0069] Database Write Queue

[0070] System Error Logs and Error Daemon

Laser Read and Write

[0071] The first module consists of socket communication read and writesprograms. The write program outputs commands to the laser. The readprogram acquires the responses and data from the laser. A masterscheduler module calls the write program at configurable periodicintervals. The read program is called depending upon the availability ofthe response data from the device. Each write operation will initiate adata response from the device. The subsequent write operation to thesame device should not be attempted before a successful acquisition or atimeout value on the read operation.

Command Write to Device

[0072] A socket connection is made from the Linux server to the terminalserver. Commands are written to the socket under the control of themaster scheduler.

[0073] A preferred list of commands to the device is given below:

[0074] Get Configuration

[0075] The laser control system uses configurable data to customizesystem operation. For example, the amount of gas during a refilloperation, the ages of many laser components, the laser serial number,and many other parameters are included in configuration data. The “getconfiguration” command collects this information.

[0076] Get Diagnostic

[0077] Inside the laser, sensors monitor the laser's performance.Periodically, the control module reads the sensors and updates thememory locations that are used to store the sensor readings. Thediagnostic readings include parameters such as the temperature insidethe laser, and the cooling water flow rate.

[0078] Get Errors

[0079] When the laser detects warnings or errors, it displays a messageon the hand-held terminal, and logs the warning/error code in a sectionof reserved memory. Each log entry contains the warning or error codenumber, the date and time that the error occurred, and the parameterthat caused the error. The laser stores up to 50 warnings (if you arerunning MCS version 1.64 or later) and up to 50 errors.

[0080] Get Status

[0081] Status data are the parameters that determine laser performance,such as repetition rate, energy mode, trigger mode and burst count.

[0082] Get Shot data

[0083] Every time the laser fires, the following information is saved inthe main control board:

[0084] Pulse energy

[0085] High voltage setpoint

[0086] Wavelength

[0087] Bandwidth

[0088] Get Averaged Shot data 1K

[0089] This is shot data averaged over 1000 pulses

[0090] Get Averaged Shot data 100K

[0091] This is shot data averaged over 100,000 pulses

[0092] Get Averaged Shot data 100M

[0093] This is slot data averaged over 100,000,000 pulses

[0094] Get Fringe Data

[0095] Fringe data is a 1024-byte spectral representation of a singlelaser shot and is used for wavelength calibration. Unlike the other datatypes, valid fringe data can only be downloaded while the laser isfiring.

[0096] Get All

[0097] This instruction acquires all of the above data. The lasersoftware stores command characters until it encounters a terminatingsignal. The software then gathers and sends the data to the centralcontrol server unit.

Command Write Queue

[0098] The master scheduler sends commands to a write queue at ascheduled time. Additionally, an interactive user or another controlprogram can send commands to the command write queue. The write queueuses a first in first out structure and sends the commands to the deviceusing sockets. Commands are issued to a specific laser as designated.The next command to the same laser should not be attempted until theprevious command has been completed or a timeout has occurred. Data fromthe parser is passed to the calling program in an XML format file. Thefile handler is returned to the calling program by a return messagequeue. The master scheduler does not need returned data. The returneddata is then submitted to a database write queue for uploading of thecollected information into the database.

Data Read from Device

[0099] Each command sent to each laser results in a response with datafrom the laser. The subsequent command can be written to the laser afterthe data response for the previous command has been completely received.If there is no response from the laser, the resulting timeout willterminate the data read program and append an entry to the system errorlog. Data is read from the terminal server using a socket connection. Aform feed denotes the end of each data response. The parser applicationwill handle the entire data response as one dataset. The primarydifference here is that only the first data set will have the laser ID.For the purposes of data validation of the data read program, the datais treated as one long string of printable ASCII character. Anon-printable ASCII character indicates corrupted data, and that dataset will be discarded with an entry to the system error log. Validateddata is passed to the parser program in preparation for database loadingor web viewing by an interactive user. Other programs that call thewrite queue module will receive the data in XML format from the parser.

Master Scheduler

[0100] This program schedules the various command writes to the laser atpreviously configured time intervals. Users maintain the commandfrequency using a User Interface Screen (on the web). The command-writeoperation to a laser results in a data response. The Linux standard“cron” utility will be used as the master scheduler. A user interface isprovided to view and modify the contents of the “crontab” file. A normaluser account is used to run these cron jobs.

Interface to the Parser

[0101] A laser read program calls the parsing program when it has acomplete set of data responding to a command. If the response data isincomplete after a timeout period or is corrupted, it is discarded. Ifnot, the response read from the laser will be stored in a disk buffer.

[0102] The parsing program analyzes this data, parse the data perpre-defined grammar and prepare it to load into an Oracle database. Theparsing program will then issue a database write request to a databasewrite job queue.

Database Write Queue

[0103] Database write requests from the parser are stored in a jobqueue. Load commands are initiated based on the capabilities of adatabase SQL loader. The input data rate over a period of time shouldallow for completion of all the database write requests asynchronously.

[0104] A database write submits a job in the batch queue. Commands willbe provided to monitor, delete and add new jobs to the batch queue. Whena job terminates, the exit value will indicate a success or an errorsituation. It is possible to use the Linux operating system shellscripts to perform an asynchronous job control of batch jobs. The job tobe run in the background under the local shell, and the shell willnotify the main program when the job has a change in status. When thequeue details program is used in the more traditional batch-processingenvironment, results are returned to the user via e-mail. These resultsare redirected to the appropriate success or error log files.

System Error Logs and Error Daemon

[0105] The application will create error log entries under the followingsituations:

[0106] No response from device for a command

[0107] Incomplete response from device with a timeout

[0108] Corrupted response from device

[0109] Database load error due to a unique key violation, where data isalready available

[0110] Database load error due to an incorrect load file

[0111] Database load error due to a database down or other systemproblems

[0112] Fatal and non-fatal errors are monitored, and appropriatewarnings are displayed in a system console window. A separate systemerror log daemon may or may not be necessary. Any new fatal or non-fatalerror occurrence will trigger alarms and console displays based on thetype and the count of errors.

Simulation Program

[0113] A simulation program to test the modules described above withouttying up a laser is preferably provided. Such a simulation programshould simulate device responses to various commands, includingincomplete responses, lack of response, and other error conditions. Thesimulation program preferably runs on a low-power, low-speed PC runningRed Hat Linux 6.2. It will be connected to the Black Box CompactTerminal Server (BBTS) using the RS232C interface. The PC stores andsimulates all standard responses for each of the possible commands.Initially, flat responses are returned. External application programinterfaces will be provided to the Command Write queue and the parseroutput as described below:

[0114] Command Write Queue. This accepts commands from the cronscheduler, an interactive intranet web user or an external program. Thisqueues the commands and writes them to a particular laser, when the lastcommand to that laser has completed. The calling program passes thecommand, device identifier and the source of the calling program to thecommand write queue.

[0115] Data Read Queue: When data has been read from the laser, it ispassed to the parser. The parser splits various fields, insertstimestamp and other headers and prepares the record as outlined in thedatabase schemas. Data read queue contains the file pointer and thereturn address for the calling programs. The calling program picks upthe data through the data read queue.

[0116] Database Write Queue: Periodic cron commands will request fordata of certain commands to be acquired and be loaded into the database.The output of the parser in SQL Loader format will be presented to theDbwrite Queue. This queue handles invocation of SQL Loaders and properloading of data.

Queue Implementation

[0117] The following queue mechanisms can be utilized:

[0118] 1. Linux Shell Queue and GNU Queue Programs

[0119] 2. TIBCO Queuing Application

[0120] 3. IBM MQSeries for Linux V5.1 Technology Release

Parser Module

[0121] The parser module creates the necessary digital information inthe appropriate form so that the data acquired can be properlyprocessed, stored and retrieved. In a preferred arrangement, theinformation is parsed into 12 categories:  1. header comprising commandand laser S/N  2. detail for identifying manufacturer data  3. xml  4.equipment identification  5. data set identification  6. sequence  7.global unique identifier  8. data set date  9. universal time codeoffset 10. connector type 11. process ID for parser status 12. name oflog for warning or error messages

User Interface—Web Pages

[0122] The web pages are displayed by constructing HTML pages on theserver 8 shown in FIG. 1. Standard HTML tags will be used to createthese pages. Since these HTML pages will contain dynamic data that willbe retrieved from the database, it is recommended that the Java ServerPages technology (along with servlets) be used. Some of the reasons forselecting this technology are as follows:

[0123] 1. JSP employs Java and related technology that have become astandard in the industry. Hence it enjoys support from a number ofvendors and has good quality of support available. Migrating to futureversions will also be easier.

[0124] 2. Tomcat, which is a JSP and servlets engine is freely availablefrom Apache (http://jakarta.apache.org/tomcat/index.html) and readilyintegrates with the Apache web server.

[0125] 3. Future extensions to display the device performance data inhand-held devices can be readily accommodated using the Xalan technologythat integrates well with the Apache web server.

[0126] Further, Java is a platform independent, secure, network friendlylanguage that employs the “write once, run anywhere” principle. Futuremigration to a different platform will not require recompilation of anyof the front-end code.

[0127] In order to support the creation of HTML pages through JSP, Javabeans are designed to support the data that needs to be displayed inthese pages. There is preferably one Java bean per JSP to load data,perform any data processing and store data back into the database.Proper methods should be identified so that the display and dataprocessing will be correctly separated between the JSP and the Javabean.

[0128] In order to access the database to retrieve/store data, JDBCtechnology is used by the Java bean. There are a number of good pureJava JDBC drivers for Oracle (level 4 drivers) that supply goodperformance. In addition, the use of prepared statements will enhanceperformance for frequently executed queries. As specified before, theJava beans contain all the logic for accessing the database. In order toenhance performance even further, these Java beans should obtainconnections to the database from the connection pool. The connectionpool will recycle connections between various calls to the database thuspreventing frequent opening and closing of the connections, which arevery expensive. The connection pool will be designed in such a way thatits parameters can be externally controlled through a text file. Some ofthe connection parameters are: number of times a connection can be used,inactive time period after which connection will be returned to thepool, etc. The reader should note that XML pages may be generatedinstead of HTML pages (from the JSP) so that data can be displayed invarious devices (palm pilot, cell phones, browsers, etc.) using theappropriate style sheets.

Web Pages

[0129] Web pages that preferably are displayed are:

[0130] 1. Administration Page—This page will be used to administer thedevice cluster connected to a particular server. Administrationfunctions will include adding a device to the network, configuring datacollection parameters, etc.

[0131] 2. Central Page—Displays the status of all the lasers that areconnected to a particular server.

[0132] 3. Summary Pages—Displays data regarding a particular lasermodel. The type of data is either cumulative or averages for that lasermodel. It also shows the number of parts that are expected to bereplaced on a weekly basis for the next 5 months.

[0133] 4. Equipment Control Pages—Displays data regarding a particularlaser ID regarding usage, maintenance and replacement schedules, etc.

[0134] 5. Service Log Pages—Data is entered by the service personnel fora particular laser ID. The details regarding the down time, partsreplaced and comments are entered in this page. This is one of the twopages in the current project which accepts data from the web user to bestored in the database (the other being the Administration page).

[0135] 6. SPC (Statistical Process Control) Pages—Displays the X-bar andRange charts for various parameters (bandwidth, energy sigma, etc.) fora particular device ID. Also displays the error and warning logsrecorded during the past 5 days.

[0136] 7. Error Pages—Errors and Warnings for a particular device ID.

[0137] 8. Comments Pages—For each device ID. (drill down from EC)

[0138] 9. Parts replaced—For each device ID. (drill down from EC)

[0139] 10. Interactive User Command Page—The user can also issues thelaser data acquisition commands like GA, GE, GD, etc. from the browser.This page will have a choice box to select the type of command and abutton to submit this command. Once the command is submitted, the rawdata that was collected will be displayed in a tabular form.

[0140] Additionally, some of these pages should contain tabs to displaydifferent types of data. For example, the summary page can be dividedinto four tabs titled Cost of Consumables, Device Productivity, DevicePerformance and Replacement Schedules. Dividing a complex page intoindividual tabs (which will be implemented as separate pages internally)will deliver faster perceived performance since the calculations torender the charts will be divided among the pages.

Web Page Sequence

[0141] The home page for the project is provided. The user can drilldown to either an individual laser by clicking on the desired device IDarea (EC, Service log, etc.) or to the summary page from this page.

[0142] There preferably are a number of links from each page to otherpages. Also, within the pages that display the details regarding aparticular laser ID or in the summary page that displays the dataregarding a particular laser model, a different laser ID or model can bechosen from a drop down list box. This event will trigger data for thatparticular ID(or model) to be displayed.

[0143] Currently, all the historical data is displayed for the past 6months. A future enhancement can provide the user with a choice toselect longer time periods (9 months, 1 year, etc.). Perhaps the mostimportant form of displaying data in this project is through the use ofcharts. The charts must be rendered on the server side and displayed onthe browser. In order to achieve this, we can either develop customizedcharting package or leverage existing charting components from thirdparty vendors. Though developing proprietary charting tools is idealsince it can be customized to our requirements, it can be very timeconsuming and expensive. A number of vendors supply Java chartingcomponents packaged as Java beans. Examples include PowerChart fromProtoView, Jclass components (JCChart) from KL Group, DataVista Pro fromVisualize, Inc., (www.visualizeinc.com) etc.

Chart Types

[0144] The following are the different types of charts that will berequired to be displayed for the project.

[0145] 1. Bar Charts

[0146] 2. Stacked Bar Charts (for cumulative data)

[0147] 3. Line Charts

[0148] 4. Line Charts with standard deviation (hi-lo) markers

[0149] 5. Scatter plots

[0150] The following table shows the preferred charts that may bedisplayed and their chart types. Page Chart Name Chart Type CommentsSummary Actual Chamber Bar chart Plot of number of chambers Lifetimereplaced vs. lifetime for a particular laser type Actual LNM Bar chartPlot of number of LNM Lifetime replaced vs. lifetime for a particulartype of laser Actual Bar chart Plot of number of stabili- stabilizationzation modules replaces vs. Module Lifetime lifetime for a particulartype of laser Current Month Bar chart Plot of usage (Million Laser UsageRate pulses) vs. number of lasers for a particular laser model MonthlyAverage Line plot Plot for last 6 months for Laser Usage Rate theaverage usage rate for a particular laser model. Monthly Uptime/ StackedFor a particular laser Downtime bar chart model, percentage of uptime,scheduled and un- scheduled downtimes for the last 6 months. MonthlyAverage Line Plot Average bandwidth for a Bandwidth and 3 with hi/loparticular laser model for Sigma Range points for the last 6 months.sigma Monthly Average Line Plot Average energy stability for EnergyStability with hi/lo a particular laser model for and 3 Sigma for sigmathe last 6 months Range Errors and Bar chart Occurances of differentWarnings Pareto (with line types of errors and Chart plot for warningsduring the cumulative?) last 6 months. EC Usage Line Plot Usage(billions of pulses) over the last 6 months for a particular laser IDSPC X-bar Line Plot Plots for Bandwidth, with UCL Energy Sigma, DoseError, and LCL Voltage, Chamber Pressure, limit lines Temperature, TotalInjec- tion Shot, F2 Consumption for a particular laser ID. Range LinePlot Same as X-bar with UCL and LCL limit lines

[0151] The tables that need to be displayed are the following: PageTable Title Row Column Data Type Summary Weekly Parts Part Name WeekNumber of Replacement (beginning parts to be Schedule date) replaced ECEstimated Part Name Week Color coded Usage (beginning cell Rate (nextdate) 5 months) Scheduled Types of Times and Times (hr) and uptime,downtimes/ percentages percentages. scheduled/ uptimes for the lastunscheduled 3 months and downtime 12 months SPC Error Log Error/Warningand Warning Type and Log description

[0152] The charts such as those of FIGS. 2 and 3 on charts portrayingsome or all the information listed above is preferably added to awebsite created in server 8 and charts are made available through theInternet to interested parties having authorization to access theinformation. Preferably this is accomplished in the well-known Internettechnique requiring a user name and a password.

[0153] Thus, this information on web server 8 is available to the lasermanufacturer and is used by manufacturer to plan maintenance andreplacement activity and to look for trends which could indicate designproblems. The information is also available to interested partiesoutside the fabrication plan but within the corporate organization ofthe owner of the fabrication plant.

External Interface Specifications

[0154] XML format where appropriate are used for communicating with theexternal applications.

Highlighting Problems and Opportunities

[0155] The system described herein permits interested parties to quicklyand efficiently compare the performance of a large number of similarlasers. This permits the parties to identify the best and worstperforming lasers and to identify problems and recognize techniques andoperating parameters which can be applied to improve performance. Forexample, it is known that the charging voltage needed to produce adesired pulse energy (e.g. 10 mJ) increases as the fluorineconcentration decreases at constant chamber gas pressure so thatcharging voltage (which is monitored for each pulse) is a qualitativemeasure of fluorine concentration (Actual quantitive measurements offluorine concentration are not made during operation.) It is thereforepossible to operate these lasers over a relatively wide range ofcharging voltage and fluorine concentration, and it is often not clearto laser operators where the most desirable operating range is.Operating within the best range is important since beam qualityparameters vary as a function of fluorine concentration and chargingvoltage. With this system, comparisons of these beam quality parameterswith charging voltage for a large number of lasers over wide ranges ofcharging voltage may permit interested parties to identify the bestrange of charging voltage for providing desired beam quality results.Chamber gas pressure can also be adjusted which would also result in acorresponding change in charging voltage or fluorine concentration forthe desired constant pulse energy and such an adjustment could improvebeam quality.

[0156] Also this system will permit the lasers to be programmed tocollect laser beam quality data during fluorine gas refills which wouldpermit a determination of beam quality values as a function ofquantitive values of fluorine gas concentration, and/or as a function ofchamber pressure. This information could be collected from a largenumber of lasers and would provide additional valuable information whichcould be used to recommend operating ranges which would produce improvedbeam quality.

[0157] While the invention has been described above with specificity interms of preferred embodiments, the reader should understand andrecognize that many changes and alterations could be made withoutdeviating from the spirit of the invention. Also, in preferredembodiments the laser manufacturer's server 16 is connected through theInternet to many fabrication plants so that hundreds of lasers aremonitored. For example, the terminal server 6 shown in FIG. 1 could be anetwork card embedded in the laser 2, this is referred to as an embeddednetwork card. Therefore, the scope of the invention should be determinedby the appended claims and their legal equivalents.

1. A system for monitoring lithography lasers at at least one integratedcircuit fabrication plant, said system, comprising: A) a plurality oflasers each being configured for use as illumination sources in anintegrated circuit lithography process, B) a terminal server associatedwith each one of said plurality of lasers; C) a central fabricationplant server unit in communication through a local area network witheach of said plurality of lasers; said central fabrication plant unitbeing programmed to acquire data from each of said lasers and to storeat least portions of the data in raw form and/or summary form; D) asecond server unit providing communication through a communicationnetwork between said first server unit and computers utilized by personshaving access authorization to the information stored by said firstserver unit:
 2. A system as in claim 1 wherein said plurality of lasersare narrow band excimer lasers.
 3. A system as in claim 1 wherein eachterminal server is provided with a unique internet address.
 4. A systemas in claim 1 wherein said second server is located at facilities of alaser manufacturer.
 5. A system as in claim 1 wherein said centralfabrication plant server unit is programmed with software created inmodular form said software comprising: (a) a data acquisition module (b)a parser module (c) a database module and (d) a user interface module.6. A system as in claim 5 wherein said data acquisition module comprisessoftware components comprising: (a) laser read and write (b) commandwrite to lasers (c) command write queue (d) data read from lasers (e)master scheduler (f) interface to parser (g) database write queue (h)system error logs and error daemon
 7. A system as in claim 1 whereindata acquired from said lasers is presented at a web site created bysaid central fabrication plant server unit.
 8. A system as in claim 7wherein said data acquired from said laser is presented in the form ofsummary charts.
 9. A system as in claim 7 wherein said web sitecomprises web pages.
 10. A system as in claim 9 wherein said web pagescomprise: (a) an administration page (b) summary pages regardingparticular lasers (c) service log pages (d) error pages
 11. A system asin claim 8 wherein said charts comprise: (a) chamber lifetime charts (b)LNM charts (c) Stabilization module charts (d) Uptime or downtime charts(e) Maintenance related charts
 12. A system as in claim 1 wherein saidcommunication network is the Internet
 13. A system as in claim 1 whereinsaid communication network is an intranet system.
 14. A system as inclaim 1 wherein said terminal server is an embedded network card.